Earthmoving and construction type vehicles, which have endless self-laying track chain assemblies for support and propulsion, utilize a sprocket wheel to engage and drive the track chain. The sprocket is generally driven through a final drive planetary gear reduction assembly, which reduces the rotational speed of the transmission output shaft while increasing the torque available at the sprocket wheel. Many types of final drive assemblies have been used in the past including those having both single and double planetary gear reduction units, and those having no planetary assemblies.
One type of final drive assembly for a crawler vehicle is disclosed in U.S. Pat. No. 4,392,396 issued to Y. Sato et al. on July 12, 1983. In this patent, the input shaft rotates the sprocket through multiple gear connections, a planet carrier, gear shifts, and a torque tube. These multiple gears and shafts require several sets of bearings to provide rotational support within the stationary housing and between the gears and shafts. This assembly also utilizes several bolted joints, some of which are subjected to high torque shear loads.
Another type of final drive assembly is disclosed in U.S. Pat. No. 3,802,289 issued to M. E. Creek on Apr. 9, 1974. In this patent, a final drive gear train transmits power from a hydrostatic drive motor to a track driving sprocket. This disclosure relates to a two piece housing which is bolted together and to means for securing the various gears in place while the sprocket and outside cover are removed. This design requires a plurality of tapered bearing assemblies for rotatably supporting the various gears and closely machined mating surfaces for properly preloading the bearing assemblies. The splines securing the drive sprocket to the mating shaft must also absorb bending loads generated by the track assembly. Also, this final drive is not a planetary reduction type final drive, which the subject invention relates to.
The present invention is directed to overcoming one or more of the problems as set forth above.